1. Field of the Invention
This invention relates to the field of furnaces. More particularly, this invention relates to the field of auxiliary heating devices for supplementing the performance of furnaces in home heating systems of the hot water type.
2. Description of the Prior Art
Typically, a home heating system of the hot water type includes a heat source, a water circulation system for passing cool water near the heat source, conducting the heated water to remote radiators, and returning the water to the heat source for reheating, a water temperature sensing device for controlling the rate of combustion in the heat source, and a thermostat for controlling the rate of circulation throughout the system. Generally, the heat source is a furnace which burns a high grade fuel such as natural gas, oil, or high grade coal. Such fuels are characterized by their steady, easily adjustable rate of combustion. Such fuels are also characterized by their relatively high cost, which is steadily increasing.
It has therefore become desirable to find ways of utilizing lower grade, less expensive fuels to heat homes -- not only to save costs to the home owner, but also to conserve our supplies of precious, fossil fuels.
Efforts to utilize such low grade fuels in conjunction with already existing heating plants have not proved altogether satisfactory. For instance, U.S. Pat. No. 2,480,883 to Schramm discloses two complete furnace systems in a complex linkage with one another, one system burning a higher grade fuel than the other. Such a system requires two complete sets of pumps, water temperature sensing means, relay systems, etc. and has to be installed as a unit at the time of original construction of the dwelling, or else requires a major remodeling job to install in an existing structure. The patent of Cleer, Jr., U.S. Pat. No. 3,958,755, discloses a simpler system which utilizes a conventional wood burning fireplace-type structure having a water chamber surrounding an open fireplace, so as to use the heat from the fire to heat water circulated through the existing heating system. Cleer, Jr., however, does not provide any means for controlling the rate of combustion of wood in his fireplace, short of tending the fire manually, a time consuming job in itself.